In a survey of 125 people, 45 said they did not approve of spending tax dollars for a sculpture in front of city hall. how many people out of 25 could be expected not to approve

This is a ratio ...

45 out of 125 did not approve. That is written

45:125 or 45/125

you want to find how many out of 25 which would be written

x:25 or x/25

now we can compare

45/125 = x/25

if we divide 125 by 5 we get 25 so we need to divide 45 and 125 by 5 to get the answer.

45/5 = 9

125/5 = 25

Your new ratio is

9:25 or 9/25

9 of 25 people don't agree.